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Old 07-30-2018, 03:17 AM   #1
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Insulating Bulk-Head on Axis

So I did some more Mods this weekend after reading a few AC threads. I was going to post with one of them but I knew this would be a long one and I didn’t want to get it lost in the shuffle. Plus it’s not about the AC unit at all. - Its about making the cab area more insulated for hot and cold and to reduce road/wind noise.

These tips were mentioned by a few Thor Forum Members - so I cannot take credit for them - but I wanted to share what I did and the overall results.

The Bulkhead above the dash (Over the windshield and next to the drop down bunk on my Axis) is not insulated at all – its just a hollow dead space. Like I mentioned - a few members pointed this out – Its Just open space and you can see the fiberglass roof. This area is around 7 foot long - 10 inch deep and 12 inches wide or so - then I have about an inch space (It varies) between the inner ceiling and the outer fiberglass roof. So after inspecting this area I decided to make a trip to Home Depot to look for some insulation that might work. I spent about 30 bucks (plus about $100 on Amazon for Kill Matt and Fat Mat – I love this stuff – but its pricey).

When I looked into this bulkhead you can feel the tops of the A Pillars are empty (but on my unit the factory used foam to fill the under lower ends that connect inside engine compartment - so that was good). I took two foam pipe insulators then covered with some Frost King batting with aluminum backing (held on with duct tape) and shoved them down into the A pillars - cut to fit then bent down some to shove in the hole. This took some time – very tight fit.

Next I used some Killmat (half the price of Dynomat but is a little thinner but not as sticky) and covered fiberglass roof part (including the tops of A pillars). I went as far back has I could stick my hand into the smaller spaces.

Then I used the 1/2-inch Styrofoam board (4 x 8 sheet) that has an aluminum backing. I cut that into aprox 2 foot x 6 foot strips so I could slide one at a time in-between this section. I was able to curve it down to the very front bottom part of this bulkhead.

Next I installed the 3/4 inch Fat Mat in the main area only and over the A pillars,.

Followed up with some Frost King (2 inch thick aprox 15 inch wide batting with aluminum backing).

Then I thought why not used some left over Frost King over the batting - but this is the kind that is thin with sticky back and aluminum top side.

Lastly put some leftover non-fiberglass batting in every crack and crevice that I could reach over the bunk area.

So if you were counting 5 layers thick with some extra batting in spots! (most with aluminum backing on them!) All of them with different densities and thicknesses. I figured more is better – Right?

The results – hard to say rigth now. On the interstate I think it help slightly – But I only went about 10 miles or so - might find better results on a windy day? Heat wised I don’t know yet – it was a cool cloudy/rainy day today. So will have to check on that later. I like to think it will help some in the summer and wintertime. Im still glad I insulated it - Im trying to eliminate any areas that can build up heat or radiate noise with driving.

Conclusions. Not sure how much good it did - But I think it was worth it. I think if I just used the Styrofoam board with some non-fiberglass batting and maybe a layer of frost king with aluminum backing it would be just as good and only cost like $30 bucks and I think that would be good enough (along with my A pillar insulation).

Total job took about 4 hours including cleanup.

Oh yeah, I installed some 12 gauge wires for my next project - 12 volt fan in the cockpit area. You can see from the pictures the factory had a 1-inch hole already drilled for it.
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Old 07-30-2018, 03:19 AM   #2
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More pics
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Old 07-30-2018, 07:39 PM   #3
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Two more thought on this.

One - With the bunk in the up position I don’t think you will notice the extra insulation that I installed but in the down position im sure it will make a difference since there is none in this area.

TWO - I wish I turned on my AC while working in this area (I bet I would have felt the air flow in the bulkhead area). I suspect the factory air channels in the ceiling just dump air in this area since I have realized a significant increase in air flow at the ceiling registers that I modified.
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Old 08-02-2018, 04:12 AM   #4
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Really, 432 views and not one single comment? I thought a few folks would chime in on this one. I bet I can post something about pets or black tank I would get 3 pages of comments in two days.

Oh did I mention I cant find my cat now?? But when back up the RV it meows. And it sounds like it over my head.
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Old 08-02-2018, 11:13 AM   #5
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Sounds like a good project. Noise damping and insulation are both a good investment. I plan on working above and below cab area once weather cools some. I can see looking down duct with mirror that there are gaps at end of ducts. I am planning on sealing those as well.

Good job.
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Old 08-02-2018, 11:20 AM   #6
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What I find is that you'll get comments when other people decide that they want to also do that project on their RV. Since this one is a little bit more involved than your average project (at least add on project, not like the emergency fix the crappy wire nuts projects LOL) and thus people may not be willing to do it.

As an example, take a look at my DIY capacitive tank sensor project. Most of the posts in that thread are me and one other individual who was also interested in doing something similar.

My question about this project: How easy is it to get up there? Is it just that one panel you have to remove in front of the roller shade? (Do you have to remove the roller shade to get in there?)
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Old 08-02-2018, 11:40 AM   #7
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The amount of wood and particle board used to make that cab amazes me.
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Old 08-02-2018, 12:11 PM   #8
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Yes, very discouraging. In an accident all that wood isn’t going to deform like steel sheets. On the other hand wood (plywood, etc.) has better insulation (thermal and sound) properties than steel. There was a previous thread showing extensive use of wood in cab area that was very revealing.
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Old 08-02-2018, 12:48 PM   #9
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Originally Posted by JamieGeek View Post
What I find is that you'll get comments when other people decide that they want to also do that project on their RV. Since this one is a little bit more involved than your average project (at least add on project, not like the emergency fix the crappy wire nuts projects LOL) and thus people may not be willing to do it.

Good to know - Yeah I bet you right.

As an example, take a look at my DIY capacitive tank sensor project. Most of the posts in that thread are me and one other individual who was also interested in doing something similar.

I can see that.

My question about this project: How easy is it to get up there? Is it just that one panel you have to remove in front of the roller shade? (Do you have to remove the roller shade to get in there?)
Very easy, Just removed the side curtain tracks and let dangle, removed trim buttons that cover the 6 wood screws.



Thanks for post background info.

Do me a favor, when you open up the bulkhead, turn your AC on and let me know if the ducts are blowing cold air in that area. I already blocked off my vents (Big improvment of airflow - put on your must do list) and I really dont want to remove insulation to test my theory.
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Old 08-02-2018, 12:53 PM   #10
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Originally Posted by Chance View Post
Yes, very discouraging. In an accident all that wood isn’t going to deform like steel sheets. On the other hand wood (plywood, etc.) has better insulation (thermal and sound) properties than steel. There was a previous thread showing extensive use of wood in cab area that was very revealing.
Yep, I think your right. Wood will dampen some sound and temps. I think I went overkill on the insulation part but at the time I didnt know for sure - and since I already had this area exposed I thought Im going to fill it. Once I take a trip I can verify my findings.

If I was handy with cabinet making I would rig up some sort of trap door to drop down for more storage or a hiding spot. Might still do that down the road - im willing to learn. Thanks for the reply.
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Old 08-02-2018, 12:55 PM   #11
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Originally Posted by The Gritz Carlton View Post
The amount of wood and particle board used to make that cab amazes me.
Yep, for sure. I just wish the Thor employees could put all the screws and staples in straight and use all of them instead of hiding them under dinettes and cabinets. LOL.
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Old 08-02-2018, 02:28 PM   #12
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Originally Posted by Long & Winding road View Post
Do me a favor, when you open up the bulkhead, turn your AC on and let me know if the ducts are blowing cold air in that area. I already blocked off my vents (Big improvment of airflow - put on your must do list) and I really dont want to remove insulation to test my theory.
I sort of already blocked off mine with duct tape:
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But that is easy to remove and I want to do a better solution--and carve the ramp into the foam and modify the ducts like you & gmtech did.
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Old 08-02-2018, 02:54 PM   #13
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Originally Posted by JamieGeek View Post
I sort of already blocked off mine with duct tape:
Attachment 11969
But that is easy to remove and I want to do a better solution--and carve the ramp into the foam and modify the ducts like you & gmtech did.
Yep, it really increased the air flow esp in the front vents (I did my rear vents as well). I might add two more to the front area but Im going to wait until its gets hot again so I can determine if needed.

If you do the bulk head - rip out the tape and let me know if they are connected (I bet they are). Thanks.
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Old 08-11-2018, 11:31 PM   #14
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Good idea. Sound insulation is surely lacking on the Axis/Vegas. I did solve the heat problem fairly easily. Lined the inside of the doghouse with aluminum/dense/foam. Self sticking variety about 3/8 inch thick.. Fat mat, etc. may be better but I found some at Home Depot in the plumbing dept. It really cut down the heat and some noise. Hardest part was removing all the screws on the doghouse!
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Old 08-13-2019, 03:51 PM   #15
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I thought I would refesh this thread in case other folks are interested in insulating the Bulk Head area.

I hear that the ACE bulk head is NOT insulated as well..... so some of these mods will translate to any RV that has large empty voids up front.

Updates on my results: So far so good. I really "think" it helps to keep out the heat and cold (some) and I would "like to think" it absorbs sound but hard to say from the drivers seat.

One might get by with less expensive insulation but make sure you block the heat with some sort of aluminum backing insulation first then follow up with non fiber glass batting (like your house has) then put a barrier on the back of the bulk head cover for best results.

But I think all of in insulation mods have a cumulative
effect on heat, cold and sound.
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Old 08-13-2019, 04:38 PM   #16
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Here is something my wife found yesterday, we have an ACE 29.3, she was getting in the overhead cabinets and said she could feel cold air. Sure enough, where the wires are fished through for the lights and such somehow it is connected to the ac ducts. Now Im not complaining and may actually open that up a little bit, we moved most of our food to those cabinets since there is some AC in there.
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Old 08-13-2019, 05:50 PM   #17
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Here is something my wife found yesterday, we have an ACE 29.3, she was getting in the overhead cabinets and said she could feel cold air. Sure enough, where the wires are fished through for the lights and such somehow it is connected to the ac ducts. Now Im not complaining and may actually open that up a little bit, we moved most of our food to those cabinets since there is some AC in there.
Yep, the AC duct are cut into the foam for the roof insulation and they just terminate at both of the end caps (front and rear of the RV). So you need to block off the very last vent (on each side of the RV) so 4 vents total so your not wasting good AC. Plus it will boost the presure and give you more out output in the rest of the RV.

So when your AC is not on this area will get super hot and in the winter it will freeze first. So I would not put food in this area for any length of time.
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Old 08-13-2019, 07:45 PM   #18
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Yep, the AC duct are cut into the foam for the roof insulation and they just terminate at both of the end caps (front and rear of the RV). So you need to block off the very last vent (on each side of the RV) so 4 vents total so your not wasting good AC. Plus it will boost the presure and give you more out output in the rest of the RV.

So when your AC is not on this area will get super hot and in the winter it will freeze first. So I would not put food in this area for any length of time.
Thats old news, I discovered the open ducts when I insulated my Ace a year and a half ago, this leak is in the middle of the coach and is in the overhead cabinets on the passenger side over the dinette table.
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Old 08-13-2019, 08:06 PM   #19
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Thats old news, I discovered the open ducts when I insulated my Ace a year and a half ago, this leak is in the middle of the coach and is in the overhead cabinets on the passenger side over the dinette table.
Oh, well you mentioned it was cool in that area so I figured it was your AC cooling it down in directly.
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Old 08-13-2019, 08:28 PM   #20
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Oh, well you mentioned it was cool in that area so I figured it was your AC cooling it down in directly.
Im not sure what is going on here. (it is definitley from the AC ducts)
I know they rout out the roofs but surprised that it is connecting the wire runs to the ducts. Like I said I dont consider it a bad thing because our overhead cabinets get pretty warm if setting in full sun. I need to take my IR gun and check the ceiling to see if there are any other leaks. Another guy with the same coach found a leak that was blowing out into the the dome over the shower. It was not a major leak but mine also had it.
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